Transformer fault detector



Manh14, 1933. n COFFIN 1,901,701

I TRANSFORMER FAULT DETECTOR Filed Sept. 30, 1952 Fig. I.

Invetor': v DavidDCoffin,

ymm

His Atizorney.

Patented Mar. 14, 1933 UNITED STATES PATENT cornea DAVID n. comm, or CAMDEN, New JERSEY, ASSIGNOR 'ro GENERAL ELECTRIC COMPANY, A con]?oRA rIonj91v NEW YORK TRANSFORMER rapn'r' nR rEc'roR Application filed September 30, 1932. Serial No. 635,591.

, My invention relates to transformer fault detectors. There is occasionally a failure or breakdown of some part of the insulation of. a transformer. The failure may be due to abnormally high voltage conditions or to a defect in the insulation. There may be a sudden development of a serious fault but it often happens that a fault first starts as a very slight defect which does not interfere 39 at all with the normal operation of the transformer and which remains undetected for a considerable period of time. Such a slight defect may become more serious, however, and finally result in a serious breakdown is of the insulation. The general object of the invention is to provide an improved arrangement for detecting and indicating the presence of a slight defect in the transformer insulation so that the defect may be repaired before serious injury occurs to the transformer.

The invention will be explained more fully in the following description taken in connection with the accompanying drawing 3 in which Fig. 1 is a view, partly in section,

of a transformer provided with a fault detector constructed and arranged in accordance with the invention; Fig. 2 is a sectional view onthe line 2-2 of Fig. 1; Fig.

3-0 3 is a sectional view on the line 33 of Fig.

1; and Fig. 4 is an explanatory perspec tive View of a section of the transformer core and the fault detector.

Like reference characters indicate similar parts in the different figures of the drawing. The transformer shown in the drawing includes a magnetic core 10 having two winding legs 11 and 12, each winding leg being surrounded by primary and, seconds ary windings 13 which are insulated from each other and from the core. most clearly in Fig. 2, the windings 13 are cylindrical in form and each of the core legs 11 and 12 have flat side surfaces so that there is a small space 14 between each face of each core leg and the adjacent inner cylindrical surface of the inner winding 13.

A number of small fiat coils 15 are se cured in one of the spaces 14: beside each of the Winding legs 11 and 12 of the core, each As showncoil 15 being arranged with oneof its flat facesclose to the'core leg and with its axis at a right angle to the axis of the core leg and the surrounding" windings 13. The coils 15 on each core leg are connected in series and distributed uniforml along the core leg and symmetrically with :respect to its center. The coils 15 on each core leg may be held in place by a supporting strip 16 of V v insulating material such as wood. Each'set of series. connected coils 15 is connected to a a relay 17 havingcontacts which. control some suitable instrument such as a bell 18.

The turns of a transformer winding are generally distributeduniformly along the core leg which they surround and the leakage fiux follows paths which aresymmetrical with respect to the center of each core leg. Thus. the leakage flux which passes through any one of the coils 15is equal to that which normally passes through the othercoil 15 whichis symmetrically located attheother sideofthe center of the adjacent core leg. The leakage flux thus induces a voltage. in each coil 15 which is equal to the voltage similarly induced in the other symmetrically located coil. Each coil 15 is also connected so that its voltage induced by the leakage flux is opposed to the voltage induced by the leakage flux in the other symmetrically disposed coil. Thus the sum of the voltages of all the coils 15 is normally zero and the relay 17 is'not affected. 'If a small fault, such as a short circuit between two adjacent turns, develops in one of the windings 13, this will affect the distribution of the leakage flux so that thesum of the voltages in the coils is no longer zero. The unbalanced voltage causes the relay 17 to close its contacts and ring the bell 18, thus indicating the occurrence of the fault. The coils 15 are preferably disposed at the faces of the winding legs which are within the opening or window in the core as shown .95

in the drawing.

The invention provides a very simple and convenient arrangement for detecting and indicating faults in transformer windings before they become serious and it has been found that the arrangement is very sensitive to small faults. g

The invention has been explained by describing and illustrating a particular application thereof, but it will be apparent that changes mayabe made without departing from the spirit of the invention and the scope of the appended claims.

What I claim as new and desire to secure 10 by LettersPa'tent'of' the United States-is:

'1. A transformer including a magnetic core having a winding leg,a winding surrounding said winding leg, plurality of coils between said winding leg and said winding, each coil being disposed atone side of the winding leg with its axis at the right angle to that of the Winding leg,'and an instrument connected to said coils.

2. A transformer including a'magnetic core having two winding legs, a winding surounding each ofsaid winding legs, a

plurality of coils between each winding leg 7 and its winding,each coil being disposed at the side of its winding leg within the core .25 window and with its axis at a'rightangle to that of its winding leg, and means connectedto said coils and responsive to the effects ofa fault in said windings.

A'transformer including a magnetic core having a winding leg, a winding sur- I rounding said winding leg, a plurality of coils between said winding leg and said winding, each coil being disposed at one side of the winding leg'with its axis at a right angle to that of the winding leg, and each coil being disposed symmetrically to 'another coil with respect to the center of the winding leg, and an instrument connected to said coils.

4. Atransformer including ajmagnetic core having a winding leg, a-winding surrounding said winding leg, a plurality of "coils between said winding leg and said winding, each c'oil being disposed at one side of the "winding leg with its axis at a right angle to that of the winding leg, each coil being disposed symmetrically to another coil-with respect tothe center of the winding leg, and each two symmetrically disposed coils being connected with their voltages normally opposed, and an instrument connected to said coils.

In witness whereof, I have hereunto set my hand.

I DAVID D. GOFFIN 

